Fractionation of oils and fats is a well-known process for modifying the composition of natural oils. Various processes are patented by companies such as Alfa Laval, Tirtiaux, De Smet, etc. using dry, detergent or solvent technique. Natural fats are composed of complex mixtures of triacylglycrols, diacylglycerols, and minor components consisting of tocopherols/tocotrienols, sterols and other unsaponifiables. The melting and crystallisation behaviour of the oil depends on the fatty acid and triacylglycerols in the oil.
In order to obtain a more liquid fraction of palm oil, it is possible to segregate the higher melting triacylglycerols through cooling process thereby leaving the unsaturated portion of the triacylglycerols which is filtered through membrane presses. Multiple step fractionation has been recommended to obtain a much higher unsaturated olein fraction. Increasing usage of palm oil in the world markets calls for products which have high fluidity and clarity at low temperatures. It is possible by blending to achieve oils with more fluidity by blending palm olein with unsaturated oils.
Most unsaturated oils are high in linoleic and linolenic fatty acids. The exception is olive oil which is high in oleic acid and is touted as the best oil for human consumption. Moreover, with more health conscious consumers, the trend is towards having fats of less saturation and less polyunsaturation. New oils have been developed through plant engineering and breeding for such modified compositions.
It is well known among the artisans in the field of the invention that normal palm olein with iodine value (IV) of 56 has oleic content of 43% to 45%, linoleic content of 11% to 14% while that of IV 65 has oleic content of 47% to 49% and linoleic content of 14% to 16%. The saturated fatty acids content is between 29% to 31%.
Considerable attention in recent years has been paid in this field and some of the inventions have been patented. U.S. Pat. No. 4,948,811 is directed to triglyceride cooking/salad oil compositions with balanced fatty acid ester content to achieve health benefits. The fatty acid ester content of the triglyceride of the oil comprises from about 60% to about 92% oleic, from about 5% to about 25% linoleic, from 0% to about 15% α-linolenic and less than 3%, preferably less than 1% saturated fatty acids.
Both U.S. Pat. No. 5,843,497 and its continuation-in-part, U.S. Pat. No. 5,578,334, relate to fat blends and methods for their manufacture and use in foods to stabilise or lower the low density lipoprotein cholesterol (LDL or LDL-C) concentration and increase the high density lipoprotein cholesterol (HDL or HDL-C) concentration in human serum.
U.S. Pat. No. 5,874,117 features the blending of corn oil with palm oil and other palm fractions to obtain shortening blends with good resistance to oxidation. More specifically, these shortening blends are produced by simple blending of commercially available palm oil, fractionated palm oil components (the olein, superolein, stearin, and mid-fraction components), and/or palm kernel oil with corn oil. Such shortenings represent a cost-effective alternative to those produced by partial hydrogenation of vegetable oils, interesterification of fats and oils, and supplementation of oxygen-susceptible fats and oils with antioxidants.
U.S. Pat. No. 6,034,130 provides a synthetic triacylglycerol (TAG) composition which is whose composition and structure are close to those of human milk, using a synthesised process for incorporating polyunsaturated fatty acids (PUFAs) which does not cause significant destructive oxidation of the PUFAs.
Further, a research paper which was written by one of the present inventors, Dr. Siew Wai Lin entitled Crystallisation Behaviour of Palm Oleins and Some Blended Products was published during the Palm Oil Research Institute of Malaysia International Palm Oil Congress (PIPOC) held on 1 to 6 Feb. 1999. In this paper, the crystallisation behaviour of different types of palm oleins (based on IV) was discussed in relation to their chemical properties. In addition, a study on fractionation of palm oil containing small quantities of unsaturated oils was also reported. Oleins of excellent cold stability are achievable through the process discussed in the paper.